Sodium hypochlorite (NaOCI) is a highly safe colorless or light greenish yellow liquid with properties such as powerful disinfection, deodorization, and bleaching action. Thus, it is widely used for rinsing fruits, vegetables, cookware, and tableware; treating waste water and sewage; and disinfecting coolants used for boilers and power generation plants.
Sodium hypochlorite is generated by electrolyzing salt water, sea water, or natural or synthetic solutions containing sodium chloride (hereinafter referred to as “brine”). In general, electrolysis of brine with an electrolysis device yields chlorine (Cl2) by oxidation at an anode, and sodium hydroxide (NaOH) and hydrogen (H2) by reduction at a cathode. Further, the yielded sodium hydroxide (NaOH) and chlorine (Cl2) react to yield sodium hypochlorite.
In general, devices used industrially to produce sodium hypochlorite using the above described electrolytic reactions are composed of brine supply devices and electrolytic cells electrolyzing brine. To date, various types of electrolytic cells have been developed to improve efficiency of electrolysis.
As an example of conventional electrolytic cells, U.S. Pat. No. 4,372,827 (registered on 2 Aug. 1983) discloses a horizontal diaphragm-free electrolytic cell as illustrated in FIG. 1 which is included herein. Referring to FIG. 1, this electrolytic cell consists of a polyvinyl chloride (PVC) housing (1) flanked by covers (2) at both ends with a cathode terminal (3) and its connector (4) installed at one end, and an anode terminal (5) and its connector (6) installed at the other end. In addition, the anode (7) of the first cell assembly is in contact with the cathode terminal (3) such that the area indicated by reference numeral 8 in FIG. 1 becomes anodic and the area indicated by reference numeral 9 which is separated from the next cell becomes cathodic. Multiple middle cells are arranged serially in this way until the anode (10) of the last cell comes in contact with the anode terminal (5).
However, in electrolytic cells with the above described structure, electrode plates forming each cell are linked with separators (11) by using joint bolts, making the entire structure very complicated. Thus, it is very difficult to maintain a regular or constant interval between the electrode plates. In particular, insufficient discharge of hydrogen gases resulting from the electrolysis may raise safety concerns by putting the housing at a risk of explosion.
Korean patent number 592331 (registered on 15 Jun. 2006) discloses an electrolytic cell with a structure as illustrated in FIG. 2 included herein. Referring to FIG. 2, the electrolytic cell (9) consists of a cylindrical case (2) equipped with a brine supply pipe (1) and a hydrogen gas discharge pipe (6), multiple electrode plates (3) arranged side-by-side at certain intervals inside the case (2), and separators (4), which divide the inside of the case into multiple electrode chambers (5). In addition, a penetration hole (7) for expelling hydrogen gas is formed at an upper part of a separator (4) and a flow path (8), in which brine and sodium hypochlorite move, is formed within the flow path (8).
However, such electrolytic cells with the structure as shown in FIG. 2 have the following problems. The flow of brine is not smooth due to the fact that brine and sodium hypochlorite must run through each electrode chamber (5) via the flow path (8) existing in both upward and downward directions inside the separators (4). Especially, there is a need for cumbersome additional adhesion or welding work for fixing the electrode plates (3) or separators (4) each other. In addition, when the components are interconnected by welding or other adhesive inside the case (2), metallic materials or chemical components used for the interconnection may inhibit electrolysis of brine and may also deteriorate durability of the structure as a result of corrosion or short circuits at joints.